YSI 6 series Manual do Utilizador descarregar pdf (Página 20)

pHTROUBLESHOOTING

pH probes typically have a shorter life expectancy than the other sensors on your sonde. They can be

expected to last at least one year in the field when properly maintained. The two most common problems

are related to stability and slow response. These two problems aren’t always apparent when looking at

the pH millivolts during calibration.

STABILITY

The stability of a pH sensor during calibration can be affected by both static electricity and human body

capacitance. This is especially true in the winter months when static levels are at their highest. The FG

(flat glass) pH probe is especially sensitive.

The problem of unstable readings is usually solved by moving away from the sonde during the

calibration process. Holding the sonde and cal cup must be avoided when this condition exists. Try to

stand at least one meter away from the sonde when waiting for the pH to stabilize. In severe conditions

try calibrating the pH probe in a glass beaker instead of the calibration cup. If the pH probe will not

stabilize, then follow the re-conditioning procedure found in your manual.

In addition a test can be performed to confirm that the sonde pH port is not contaminated and that the pH

circuitry is working correctly. Using a 10 Meg ¼ watt ohm resistor (available at Radio Shack), insert the

resistor into the two female pins in the pH connector on the sonde. You must not hold the resistor and

will have to stand away from the sonde for a good test. With the 10 Meg resistor installed the pH milli-

volts should drop to near zero and remain fairly stable (±3 mv) If the millivolts do not stabilize with the

resistor, then there may be a problem with port contamination. Follow the port cleaning instructions at

the end of this section.

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 38 39

Sem comentários

YSI 6 series Manual do Utilizador Página 20